Low rhenium single crystal superalloy for turbine blades and vane applications

ABSTRACT

A low rhenium nickel-base superalloy for single crystal casting that exhibits excellent high temperature creep resistance, while also exhibiting other desirable properties for such alloys, comprises 5.60% to 5.80% aluminum by weight, 9.4% to 9.9% cobalt by weight, 4.9% to 5.5% chromium by weight, 0.08% to 0.35% hafnium by weight, 0.50% to 0.70% molybdenum by weight, 1.4% to 1.6% rhenium by weight, 8.1% to 8.5% tantalum by weight, 0.60% to 0.80 titanium by weight, 7.6 to 8.0% tungsten by weight the balance comprising nickel and minor amounts of incidental impurity elements.

FIELD

Disclosed are single crystal nickel-base superalloys exhibitingexcellent high temperature creep resistance, while having a reduced orlow rhenium content, without deleteriously affecting other relevantcharacteristics for many turbine engine airfoil applications.

BACKGROUND

Because of a worldwide growing demand for products that have customarilyrequired substantial quantities of relatively scarce metal elements,both the demand and prices of rare metal elements have sharplyincreased. As a result, manufacturers are searching for new technologiesthat will reduce or eliminate the need for these metal elements.

Rhenium is an example of a truly rare metal that is important to variousindustries. It is recovered in very small quantities as a by-product ofcopper-molybdenum and copper production. In addition to its high cost,use of rhenium presents a supply chain risk of both economic andstrategic consequence.

Rhenium has been widely employed in the production of nickel-basesuperalloys used to cast single crystal gas turbine components for jetaircraft and power generation equipment. More specifically, rhenium isused as an additive in advanced single crystal superalloys for turbineblades, vanes and seal segments, because of its potent effect at slowingdiffusion and thus slowing creep deformation, particularly at hightemperatures (e.g., in excess of 1,000 degrees C.) for sustained periodsof time. High temperature creep resistance is directly related to theuseful service life of gas turbine components and turbine engineperformance such as power output, fuel burn and carbon dioxideemissions.

Typical nickel-base superalloys used for single crystal castings containfrom about 3% rhenium to about 7% rhenium by weight. Although rheniumhas been used as only a relatively minor additive, it has been regardedas critical to single crystal nickel-base superalloys to inhibitdiffusion and improve high temperature creep resistance, it addsconsiderably to the total cost of these alloys.

From the foregoing discussion, it should be apparent that it would beextremely desirable to develop single crystal nickel-base superalloysthat exhibit excellent high temperature creep resistance, whilesignificantly reducing the need for rhenium alloying additions, andwhile retaining other desirable properties such as creep-rupture, lowcycle fatigue (LCF) strength and oxidation coating performance.

SUMMARY

The low rhenium single crystal nickel-base superalloys disclosed hereinrely on, among other things, balancing the refractory metal elements(tantalum, tungsten, rhenium and molybdenum) at a total amount of fromabout 18% to 19% by weight in order to achieve good creep-rupturemechanical properties along with acceptable alloy phase stability,including freedom from excessive deleterious topological close-packed(TCP) phases that are rich in tungsten, rhenium and chromium, whilesubstantially reducing the rhenium content.

It has been discovered that a low rhenium single crystal nickel-basesuperalloy exhibiting excellent high temperature creep resistance andother properties well suited for use in casting gas turbine componentscan be achieved in an alloy composition containing 5.60% to 5.80%aluminum by weight, 9.4% to 9.9% cobalt by weight, 4.9% to 5.5% chromiumby weight, 0.08% to 0.35% hafnium by weight, 0.50% to 0.70% molybdenumby weight, 1.4% to 1.6% rhenium by weight, 8.1% to 8.5% tantalum byweight, 0.60% to 0.80% titanium by weight, 7.6% to 8.0% tungsten byweight, and the balance comprising nickel and minor amounts ofincidental elements, the total amount of incidental elements being lessthan 1% by weight.

In the case of certain embodiments of the invention, the incidentalelements of the nickel-base superalloy are present at maximum amounts of100 ppm carbon, 0.04% silicon, 0.01% manganese, 3 ppm sulfur, 30 ppmphosphorous, 30 ppm boron, 0.10% niobium, 150 ppm zirconium, 0.01%copper, 0.15% iron, 0.10% vanadium, 0.10% ruthenium, 0.15% platinum,0.15% palladium, 200 ppm magnesium, 5 ppm nitrogen (generally in theform of a metal nitride or carbonitride), 5 ppm oxygen (generally in theform of a stable metal oxide), and other trace elements present inamounts of about 25 ppm or less.

In accordance with certain embodiments, the trace elements of theincidental elements in the nickel-base superalloys are present atmaximum amounts of 2 ppm silver, 0.2 ppm bismuth, 10 ppm gallium, 25 ppmcalcium, 1 ppm lead, 0.5 ppm selenium, 0.2 ppm tellurium, 0.2 ppmthallium, 10 ppm tin, 2 ppm antimony, 2 ppm arsenic, 5 ppm zinc, 2 ppmmercury, 2 ppm cadmium, 2 ppm germanium, 2 ppm gold, 2 ppm indium, 20ppm sodium, 10 ppm potassium, 20 ppm barium, 30 ppm phosphorous, 2 ppmuranium, and 2 ppm thorium.

In certain embodiments in which enhanced oxidation resistance and/orenhanced thermal barrier coating life are desired, sulfur is present ata maximum amount of 0.5 ppm, and lanthanum and yttrium are added totarget an amount of total lanthanum and yttrium of from about 5 ppm toabout 80 ppm in the single crystal components cast from the alloy.

In accordance with certain embodiments for large industrial gas turbine(IGT) single crystal applications in which a low angle boundary (LAB)strengthening of up to 12 degrees is desired, carbon is added in anamount from about 0.02% to about 0.05%, and boron is added in an amountof from about 40 ppm to about 100 ppm.

In accordance with certain embodiments, the alloy has a density that isabout 8.90 gms/cc or less, such as about 8.85 gms/cc (kg/dm³) at roomtemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are optical micrographs of castings made from thedisclosed alloys (LA-11825, CMSX®-8, test bar #N926, solutioned+2050°F./4 hours, gage area).

FIGS. 2A, 2B and 2C are scanning electron micrographs of castings madeusing the disclosed alloys (LA-11825, CMSX®-8, test bar #N926,solutioned+2050° F./4 hours, gage area).

FIGS. 3 and 4 are Larson-Miller stress-rupture and stress-1.0% creepdiagrams showing that the alloys disclosed herein have propertiessimilar to advanced CMSX-4® single crystal nickel-base superalloy havinga substantially higher rhenium content, up to 1900° F. (1040° C.).

FIGS. 5A, 5B and 5C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #A925, 1562° F./94.4ksi/211.9 hours, fracture area).

FIGS. 6A, 6B and 6C are scanning electron micrographs demonstrating thatthe post-test phase stability of single crystal test bar castings madeusing the disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #A925, 1562° F./94.4ksi/211.9 hours, fracture area).

FIGS. 7A, 7B and 7C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #A925, 1562° F./94.4ksi/211.9 hours, gage area).

FIGS. 8A, 8B and 8C are scanning electron micrographs demonstrating thatthe post-test phase stability of single crystal test bar castings madeusing the disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #A925, 1562° F./94.4ksi/211.9 hours, gage area).

FIGS. 9A, 9B and 9C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #E926, 1800° F./36ksi/246.7 hours, fracture area).

FIGS. 10A, 10B and 10C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there areno detectable TCP phases (LA-11848, CMSX®-8, test bar #E926, 1800° F./36ksi/246.7 hours, fracture area).

FIGS. 11A, 11B and 11C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #E926, 1800° F./36ksi/246.7 hours, gage area).

FIGS. 12A, 12B and 12C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there areno detectable TCP phases (LA-11848, CMSX®-8, test bar #E926, 1800° F./36ksi/246.7 hours, gage area).

FIGS. 13A, 13B and 13C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #L926, 2050° F./15ksi/285.4 hours, fracture area).

FIGS. 14A, 14B and 14C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there areno detectable TCP phases (LA-11848, CMSX®-8, test bar #L926, 2050° F./15ksi/285.4 hours, fracture area).

FIGS. 15A, 15B and 15C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11848, CMSX®-8, test bar #L926, 2050° F./15ksi/285.4 hours, gage area).

FIGS. 16A, 16B and 16C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there areno detectable TCP phases (LA-11848, CMSX®-8, test bar #L926, 2050° F./15ksi/285.4 hours, gage area).

FIGS. 17A, 17B and 17C are optical micrographs showing adequatesolutioning and/or homogenizing of an alloy casting using a shortenedheat treatment cycle (LA-11862, CMSX®-8, test bar #A926, solutioned to2408° F./8 hours, longitudinal).

FIG. 18 is a Larson-Miller stress-rupture graphs showing thesurprisingly good stress-rupture life properties of single crystal testbars and turbine blade castings made from the disclosed alloys.

FIGS. 19A, 19B and 19C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are nodetectable TCP phases (LA-11890, CMSX®-8, test bar #A926, 2050° F./15ksi (1121° C./103 MPa)/271.8 hours, gage area).

FIGS. 20A, 20B and 20C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there areno detectable TCP phases (LA-11890, CMSX®-8, test bar #A926, 2050° F./15ksi (1121° C./103 MPa)/271.8 hours, gage area).

FIG. 21 is a drawing in cross section of a single crystal solid turbineblade cast from an alloy as disclosed herein which has the facility tomachine both mini-bar and mini-flat specimens for machined-from-blade(MFB) stress-rupture testing.

FIGS. 22A, 22B and 22C are optical micrographs demonstrating that thepost-test phase stability of single crystal test bar castings made usingthe disclosed alloys is surprisingly good, and that there are negligibledetectable TCP phases (needles) (LA-11895, CMSX®-8, test bar #R926,2000° F. (1093° C./83 MPa)/12 ksi/1979.9 hours, gage area).

FIGS. 23A, 23B and 23C are scanning electron micrographs demonstratingthat the post-test phase stability of single crystal test bar castingsmade using the disclosed alloys is surprisingly good, and that there arenegligible detectable TCP phases (needles) (LA-11895, CMSX®-8, test bar#R926, 2000° F. (1093° C./83 MPa)/12 ksi/1979.9 hours, gage area).

DETAILED DESCRIPTION

The low-rhenium nickel-base superalloys for single crystal castingdisclosed herein will be designated “CMSX®-8” alloys, and will bereferred to as such herein. The term “CMSX” is a trademark registered toCannon-Muskegon Corporation for use in connection with the sale of afamily of single crystal (SX) nickel-base superalloys.

Unless otherwise indicated herein, all amounts of elements are given asa percentage by weight or in parts per million (ppm) by weight based onthe entire weight of the alloy composition.

Single crystal superalloys and castings have been developed to exhibitan array of outstanding properties including high temperature creepresistance, long fatigue life, oxidation and corrosion resistance, andsolid solution strengthening, with desired casting properties with lowrejection rates, and phase stability, among others. While it is possibleto optimize a single additive for a particular property, the effects onother properties are often extremely unpredictable. Generally, therelationships among the various properties and various elementalcomponents are extremely complex and unpredictable such that it issurprising when a substantial change can be made to the compositionwithout deleteriously affecting at least certain essential properties.

With the embodiments disclosed herein, refractory metal elements(tantalum, tungsten, rhenium and molybdenum) (Table 1) were maintainedat a total amount of from about 18% to about 19% by weight, whilebalancing the amounts of the refractory elements to achieve goodcreep-rupture mechanical properties along with acceptable alloy phasestability (freedom from excessive deleterious topological close-packed(TCP) phases—normally tungsten, rhenium and chromium rich in this typeof alloy). Chromium and cobalt amounts are targeted accordingly toensure this required phase stability. The high tantalum at approximately8% is designed to give good single crystal castability and freedom from“freckling” defects, and, along with the 5.7% aluminum and the 0.7%titanium, appropriate γ′ volume fraction at approximately 70% and lownegative γ/γ′ mismatch for high temperature creep strength, andacceptable room temperature density of about 8.85 gms/cc (kg/dm³). Thedensity of CMSX-4® is 8.70 gms/cc (kg/dm³) and PWA 1484 is 8.95 gms/cc(kg/dm³). Aluminum, tantalum and titanium are targeted at γ′ volumefraction (Vf) attainment, along with low molybdenum for good hightemperature oxidation properties. The small hafnium addition is requiredfor coating life attainment at high temperatures.

Typical chemistry for the alloys disclosed and claimed herein are listedin Table 1. However, there are certain minor variations. First, in orderto achieve enhanced oxidation resistance and/or enhanced thermal barriercoating life, it is desirable to add lanthanum and/or yttrium in amountssuch that the total of lanthanum and yttrium is targeted to provide fromabout 5 to 80 ppm in the single crystal castings made from the alloys.As another variation, in the case of large industrial gas turbine (IGT)single crystal applications where low angle boundary (LAB) strengtheningis provided up to 12 degrees, carbon and boron additions are targeted inthe range from about 0.02% to 0.05% and 40-100 ppm, respectively.

TABLE 1 CHEMISTRY (WT %/ppm) SPECIFICATIONS CMSX ®-8 ALLOY Aero engineApplications C 100 ppm Ta 8.1-8.5 Si .04% Max Ti .60-.80 Mn .01% Max W7.6-8.0 S 3 ppm Max Zr 150 ppm Max Al 5.60-5.85 Cu .01% Max B 30 ppm MaxFe .15% Max Cb (Nb) .10% Max V .10% Max Co 9.4-9.9 Ru .10% Max Cr4.9-5.5 Pt .15% Max Hf .08-.35 Pd .15% Max Mo .50-.70 Mg 200 ppm Max NiBalance [N] 5 ppm Max Re 1.4-1.6 [O] 5 ppm Max Enhanced oxidationresistance/coating and thermal barrier coating (TBC) life S 0.5 ppm maxLa + Y 5-80 ppm (In the SX castings). Industrial Gas Turbine (IGT) SXApplications Low angle boundary (LAB) Strengthened up to 12°. C 0.05%Max B 100 ppm Max TRACE ELEMENT CONTROLS - ALL APPLICATIONS Ag 2 ppm MaxHg 2 ppm Max Bi .2 ppm Max Cd 2 ppm Max Ga 10 ppm Max Ge 2 ppm Max Ca 25ppm Max Au 2 ppm Max Pb 1 ppm Max In 2 ppm Max Se .5 ppm Max Na 20 ppmMax Te .2 ppm Max K 10 ppm Max Tl .2 ppm Max Ba 10 ppm Max Sn 10 ppm MaxP 30 ppm Max Sb 2 ppm Max U 2 ppm Max As 2 ppm Max Th 2 ppm Max Zn 5 ppmMax Density: 8.85 gms/cc (kg/dm³).

The invention will be described below with respect to certainillustrative, non-limiting embodiments that will facilitate a betterunderstanding.

A 470 lb 100% virgin initial heat of CMSX®-8 alloy was melted in May2011 in the CM V-5 Consarc VIM furnace using aim chemistry to CM KH May20, 2011 (CM CRMP #81-1708 Issue 1). The heat (5V0460) chemistry isshown in Table 2.

Two molds (#s 925 and 926) of SX NNS DL-10 test bars were cast toCMSX-4® casting parameters by Rolls-Royce Corporation (SCFO). DL-10 testbar yield at 23 fully acceptable out of a total 24 cast was excellent.

These DL-10 test bars were solutioned/homogenized and double aged heattreated at Cannon-Muskegon Corporation as follows—based on prior workwith a precursor similar family alloy designated CMSX®-7.

Solutioning and Homogenization

-   -   2 hrs/2340° F. (1282° C.)+2 hrs/2360° F. (1293° C.)    -   +4 hrs/2380° F. (1304° C.)+4 hrs/2390° F. (1310° C.)    -   +12 hrs/2400° F. (1316° C.) AC (air cool)—ramping up at 1°        F./min. between steps        -   +    -   Double Aged Heat Treatment    -   4 hrs/2050° F. (1121° C.) AC+20 hrs/1600° F. (871° C.) AC

Good microstructure attainment is evident in FIGS. 1-2—complete γ′solutioning, little remnant γ/γ′ eutectic, no incipient melting andapproximately 0.45 μm average cubic, aligned γ′, indicating appropriateγ/γ′ mismatch and γ/γ′ inter-facial chemistry, following the 4 hr/2050°F. (1121° C.) high temperature age.

Creep- and stress-rupture specimens were low stress ground and tested byJoliet Metallurgical Labs, with the results to date shown in Table 3.Larson-Miller stress-rupture and stress-1.0% creep (FIGS. 3 & 4) showCMSX®-8 has similar and surprisingly good creep strength/stress-rupturelife properties to CMSX-4® alloy (3% Re) up to approximate 1850°F.-1900° F. (1010-1038° C.), with fall-off at 2050° F. (1121° C.) due toits cost saving lower Re (1.5%) content. All these properties aresignificantly higher than Rene' N-5 (3% Re) and Rene' N-515 (low Re)alloys (JOM, Volume 62, Issue 1, pp. 55-57).

TABLE 2 HEAT #5V0460 CMSX ®-8 - 100% VIRGIN CHEMISTRY (WT ppm/%) C 9 ppmCu <.001 Si <.02 Fe .010 Mn <.001 V <.005 S 1 ppm Ru <.01 Al 5.72 Pt<.001 B <20 ppm Pd <.001 Cb (Nb) <.05 Mg <100 ppm Co 9.7 [N] 2 ppm Cr5.4 [O] 2 ppm Hf .30 Y <.001 Mo .59 La <.001 Ni Balance Ce <.002 Re 1.5Ta 8.3 Ti .71 W 7.8 Zr <10 ppm Ag <.4 ppm Bi <.2 ppm Ga <10 ppm Ca <25ppm Pb <.5 ppm Se <.5 ppm Te <.2 ppm Tl <.2 ppm Sn <2 ppm Sb <1 ppm As<1 ppm Zn <1 ppm Hg <2 ppm Cd <.2 ppm Ge <1 ppm Au <.5 ppm In <.2 ppm Na<10 ppm K <5 ppm Ba <10 ppm P 6 ppm U <.5 ppm Th <1 ppm

TABLE 3 CMSX ®-8 Heat - 5V0460 Molds 925/926 - RR SCFO [Indy] - LA 11832(Joliet/CM 366) Fully Heat Treated - Solution + Double Age [DL-10s]Creep-Rupture Rupture Life, % % 1% 2% Test Condition ID hrs Elong RACreep Creep 1562° F./94.4 ksi A925 211.9 17.5 21.5 7.3 39.1 [850° C./651Mpa] B926 157.1 16.4 22.8 2.3 23.2 1600° F./65.0 ksi B925 1072.0 27.433.5 482.8 631.5 [871° C./448 Mpa] C926 983.5 26.8 33.0 407.8 536.41800° F./36.0 ksi C925 200.2 35.0 43.3 109.7 125.1 [982° C./248 Mpa]E926 246.7 44.6 46.0 120.0 140.1 1850° F./38.0 ksi E925 86.0 37.2 38.639.7 46.6 [1010° C./262 Mpa] H926 65.9 41.4 44.0 28.6 35.6 1900 F/25.0ksi H925 214.7 38.6 39.4 82.0 105.0 1038° C./172 Mpa] J926 199.6 33.239.5 65.3 93.7 1904° F./21.0 ksi J925 362.4 30.0 37.5 141.3 182.6 [1040°C./145 Mpa] K926 359.1 33.1 34.8 164.2 194.6 1950° F./18.0 ksi L925481.1 31.4 34.9 194.1 246.1 [1066° C./124 Mpa] M926 449.6 40.0 38.9166.1 211.5 Stress-Rupture Test Condition ID Rupture Life, hrs (4D) %Elong % RA 2000° F./12.0 ksi N925 1983.2 13.0 37.9 [1093°/83 Mpa] R9261979.9 24.8 33.0 2050° F./15.0 ksi R925 275.5 24.5 38.3 [1121°/103 Mpa]L926 285.4 22.9 40.4 Alternate Heat Treatment (Tmax 2408° F.) 1800°F./36.0 ksi D925 249.0 43.1 44.0 114.5 134.8 [982° C./248 Mpa] 2050°F./15.0 ksi A926 271.8 13.6 38.1 — — [1121°/103 Mpa]

Phase stability is surprisingly good with absolutely negligible TCPphases apparent in the post-test creep/stress rupture bars examined todate (FIGS. 5-16 inclusive and 22-23 inclusive).

Recent work has shown it is possible to adequately solution/homogenizeheat treat a single crystal test bar in the alloy (FIG. 17), using ashortened cycle—2 hrs/2365° F. (1296° C.)+2 hrs/2385° F. (1307° C.)+2hrs/2395° F. (1313° C.)+2 hrs/2403° F. (1317° C.)+8 hrs/2408° F. (1320°C.) AC (8 hrs shorter). Limited creep/stress-rupture properties atcritical conditions using this shorter solution/homogenization heattreatment show very similar results to the original solution heattreatment condition (Table 3 and 4) and good phase stability [no TCPphases] (FIGS. 19 & 20).

Burner rig dynamic, cyclic oxidation and hot corrosion (sulfidation)testing is currently scheduled at a major turbine engine company.

Creep/stress-rupture data for fully heat treated solution/homogenizedand double aged (DL-10s) test specimens for the disclosed alloys arepresented in Table 4.

TABLE 4 CMSX ®-8 Heat 5V0460 Heat 5V0460 - Mold 54275 - HP2 SolidTurbine Blades RR SCFO [Indy] - LA11865 (Joliet 9220/CM-373) Fully HeatTreated - Solution + double age - 2050° F. Primary age Stress-RuptureMFB Mini Bars [0.070″ø gage] (LLE) % (4D) % Test Condition ID RuptureLife, hrs Elong RA 1562° F./94.4 ksi 54275A-B 449.0 16.3 18.7 [850°C./651 MPa] 54275B-B 359.8 18.7 19.9 1800° F./36.0 ksi 54275E-B 223.443.1 45.6 [982° C./248 MPa] 54275H-B 219.1 45.1 46.9 1850° F./38.0 ksi54275I-B 74.2 46.2 47.8 [1010° C./262 MPa] 54275J-B 76.7 39.2 43.8 1900°F./25.0 ksi 54275K-B 181.8 41.2 48.5 [1038° C./172 MPa] 54275L-B 190.841.8 38.9 1904° F./21.0 ksi 54275R-B 354.0 43.9 40.2 [1040° C./45 MPa]54275O-B 599.3 39.2 45.7 1950° F./18.0 ksi 54275T-B 410.1 27.9 48.8[1066° C./124 MPa] 54275U-B 420.6 39.1 41.1 2050° F./15.0 ksi 54275X-B287.5 26.3 32.7 [1121° C./103 Mpa] 54275Y-B 205.8 22.7 25.1 MFB MiniFlats [0.020″ Thick Gage] (LTE) Test Condition ID Rupture Life, hrs %Elong 1800° F./30.0 ksi 54275A-F 490.7 41.1 [982° C./207 MPa] 54275B-F446.0 28.8 54275E-F 437.5 24.2 54275H-F 381.9 31.6 1904° F./21.0 ksi54275I-F 404.0 36.4 [1040° C./145 MPa] 54275J-F 325.1 28.6 54275K-F312.1 24.5 54275L-F 341.1 26.6

Mini-flat bar stress-rupture testing was performed on single crystalsolid turbine blades 10 (FIG. 21) cast from alloys as disclosed hereinthat have facility to machine mini-bar specimens 15 and mini-flatspecimens 20.

A Larson-Miller stress-rupture graph (FIG. 18) shows CMSX®-8 alloy hassurprisingly good stress-rupture life properties, frommachined-from-blade (MFB) mini-flat (0.020″ (0.508 mm) gage thickness)specimens, that are close to those of a CMSX-4® alloy.

The embodiments disclosed herein are non-limiting examples that areprovided to illustrate and facilitate a better understanding, the scopeof the invention being defined by the appending claims as properlyconstrued under the patent laws, including the doctrine of equivalents.

What is claimed is:
 1. A nickel-base superalloy for single crystalcasting, comprising: 5.60% to 5.80% aluminum by weight; 9.4% to 9.9%cobalt by weight; 4.9% to 5.5% chromium by weight; 0.08% to 0.35%hafnium by weight; 0.50% to 0.70% molybdenum by weight; 1.4% to 1.6%rhenium by weight; 8.1% to 8.5% tantalum by weight; 0.60% to 0.80titanium by weight; 7.6 to 8.0% tungsten by weight; and the balancecomprising nickel and minor amounts of incidental elements, the totalamount of incidental elements being about 1% or less.
 2. A nickel-basesuperalloy for single crystal casting according to claim 1, in which theincidental elements are present at maximum amounts of 100 ppm carbon,0.04% silicon, 0.01% manganese, 3 ppm sulfur, 30 ppm phosphorous, 30 ppmboron, 0.10% niobium, 150 ppm zirconium, 0.01% copper, 0.15% iron, 0.10%vanadium, 0.10% ruthenium, 0.15% platinum, 0.15% palladium, 200 ppmmagnesium, 5 ppm nitrogen, 5 ppm oxygen, and other trace elementspresent in amounts of about 25 ppm or less.
 3. A nickel-base superalloyfor single crystal casting according to claim 1, in which the traceelements are present at maximum amounts of 2 ppm silver, 0.2 ppmbismuth, 10 ppm gallium, 25 ppm calcium, 1 ppm lead, 0.5 ppm selenium,0.2 ppm tellurium, 0.2 ppm thallium, 10 ppm tin, 2 ppm antimony, 2 ppmarsenic, 5 ppm zinc, 2 ppm mercury, 2 ppm cadmium, 2 ppm germanium, 2ppm gold, 2 ppm indium, 20 ppm sodium, 10 ppm potassium, 20 ppm barium,30 ppm phosphorous, 2 ppm uranium, and 2 ppm thorium.
 4. A nickel-basesuperalloy for single crystal casting according to claim 1, in whichsulfur is present at a maximum of 0.5 ppm, and lanthanum and/or yttriumare added in an amount targeted to achieve from about 5 ppm to about 80ppm of total lanthanum and yttrium in a single crystal casting.
 5. Anickel-base superalloy for single crystal casting according to claim 1,in which carbon is present in an amount of from 0.02% to 0.05%, andboron is present in an amount of from 40 ppm to 100 ppm.
 6. Anickel-base superalloy for single crystal casting according to claim 1,having a density of about 8.90 gms/cc (kg/dm³) or less.
 7. A nickel-basesuperalloy for single crystal casting according to claim 1, having adensity of about 8.85 gms/cc (kg/dm³).
 8. A single crystal componentcast from an alloy according to claim
 1. 9. A single crystal componentaccording to claim 8 that is a gas turbine component.
 10. A singlecrystal component according to claim 8 that is a turbine blade, a vane,or a seal segment for a gas turbine.